Microstructural and electrochemical impedance study of nickel-Ce_(0.9)Gd_(0.1)O_(1.95) anodes for solid oxide fuel cells fabricated by ultrasonic spray pyrolysis

摘要

Optimization of the electrode microstructure in a solid oxide fuel cell (SOFC) is an important approach to performance enhancement. In this study, the relationship between the microstructure and electrochemical performance of an anode electrode fabricated by ultrasonic spray pyrolysis was investigated. Nickel-Ce_(0.9)Gd_(0.1)O_(1.95) (Ni-CGO) anodes were deposited on a dense yttria stabilized zirconia (YSZ) substrate by ultrasonic spray pyrolysis, and the resulting microstructure was analyzed. Scanning electron microscope (SEM) examinations revealed the impact of deposition temperature and precursor solution concentration on anode morphology, particle size and porosity. The electrochemical performance of the anode was measured by electrochemical impedance spectroscopy (EIS) using a Ni-CGO/YSZ/Ni-CGO symmetrical cell. The deposited anode had a particle size and porosity in ranging between 1.5-17 μm and 21%-52%, respectively. The estimated volume-specific triple phase boundary (TPB) length increased from l.37 x 10~(-3) μmμm~(-3) tol.77 x 10~(-1)μmμm~(-3)as a result of decrease of the particle size and increase of the porosity. The corresponding area specific charge transfer resistance decreased from 5.45 ohm cm~2 to 0.61 ohm cm2 and the activation energy decreased from 1.06 eV to 0.86 eV as the TPB length increased.